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Biomedical subjects

J Robinson

Publications and source records attributed to J Robinson.

At least 325 records · Page 18Linked to original sources
PubMed1992

Retinopathy of prematurity: a prospective study. Review at six months.

A cohort of infants of birthweight < or = 1700 g studied prospectively for retinopathy of prematurity (ROP) has been reviewed at 6 months corrected age and the findings related to the neonatal data. The overall incidence of strabismus was 6.4% (30/468), rising from 3.1% (7/229) without ROP to 29.2% (7/24) with stage 3. Strabismus and fusional ability were significantly related to presence and severity of ROP, and abnormal neonatal cranial ultrasound findings. Binocular visual acuity was measured in 340 infants between 20 and 40 weeks corrected age. Eight were subnormal, all due to neurological problems. For the remainder, despite falling within the normal range, there was a significant trend (p < 0.001) for lower acuities with increasing ROP severity. Cycloplegic refraction on 387 infants revealed, with increasing ROP severity: 1, a significant trend towards myopia; 2, increased magnitude of astigmatism; 3, alteration of the astigmatic axis; 4, increased incidence of anisometropia. For the first three categories there was an insignificant trend between no ROP and stage 2, reaching significance only between stage 2 and 3. The predominant axis of astigmatism in infants without ROP was between 60 degrees and 120 degrees, but with ROP there was a significant trend away from this direction.

Age Factors↗
PubMed1992

Light and the immature visual system.

Preterm neonates are cared for in an environment which is continuously and brightly lit, and is very different to that experienced at any other time of life. The amount of light reaching the neonatal eye is governed by two groups of factors. Physical factors include intensity, spectral characteristics and duration of light exposure. Physiological factors are: Frequency of eyelid opening, transmission of light through the closed eyelid, pupil reactivity and area, transmission by the ocular tissues and retinal surface area. Retinal irradiance declines with increasing postmenstrual age. Mechanisms by which light may affect the neonatal eye and clinical conditions in which light have been implicated are considered.

Dose-Response Relationship, Radiation↗
PubMed1992

Natural history of retinopathy of prematurity: a prospective study.

The natural history of retinopathy of prematurity (ROP) has been studied prospectively in 572 infants < or = 1,700 g birthweight using a protocol designed specifically to investigate the subtle features of this condition. Acute ROP developed in 50.9%. All ROP stages 1 and 2 underwent complete resolution and of the 27 (4.7%) infants with stage 3/4 disease, cicatricial sequelae developed in six. Incidence and severity increased with decreasing birthweight and gestational age. Onset was not confined to the temporal retina but exhibited a predilection to start first in the nasal retina of the most immature neonate. The vertical retinal regions were relatively spared. Retinal arteriolar tortuosity developed around three months postnatally and was related to ROP severity but not its presence. The age at onset and rate of progression of retinopathy were largely determined by the stage of development but were also modified by systemic and local factors. The relevance of these findings to ROP screening is discussed.

Acute Disease↗
PubMed1992

Family structure and changes in living arrangements among elderly nonmarried parents.

We used Longitudinal Study of Aging data to investigate change between 1984 and 1986 in living arrangements of older nonmarried parents, focusing on transitions from living alone and living with children to living alone, with children, with others, and institutionalization. Predictors reflect opportunities for coresidence (number and gender of children), resources, needs, and (indirect measures of) attitudes. We find that those with more children are more likely to change from living alone to living with a child. However, number of children does not affect the odds of moving from living with a child to other arrangements (including institutionalization). Gender of children does not affect tendencies to begin coresidence, although there is slight evidence of more movement out of coresidence for those with sons. Findings are interpreted in terms of the influence of adult children's and parents' needs in determining coresidence.

Aged↗
PubMed1992

The use and limitations of Phaneuf's Nursing Audit.

The use of Phaneuf's Nursing Audit in an action research project that is investigating quality assessment and peer review is discussed. A brief description of the project is given followed by an analysis of the audit tool. This analysis suggests that the tool has more disadvantages than advantages. The paper concludes with a discussion about why the tool may be of use despite the disadvantages identified.

Clinical Nursing Research↗
PubMed1992

Relationship of the human immunodeficiency virus type 1 gp120 third variable loop to a component of the CD4 binding site in the fourth conserved region.

Neutralizing antibodies that recognize the human immunodeficiency virus gp120 exterior envelope glycoprotein and are directed against either the third variable (V3) loop or conserved, discontinuous epitopes overlapping the CD4 binding region have been described. Here we report several observations that suggest a structural relationship between the V3 loop and amino acids in the fourth conserved (C4) gp120 region that constitute part of the CD4 binding site and the conserved neutralization epitopes. Treatment of the gp120 glycoprotein with ionic detergents resulted in a V3 loop-dependent masking of both linear C4 epitopes and discontinuous neutralization epitopes overlapping the CD4 binding site. Increased recognition of the native gp120 glycoprotein by an anti-V3 loop monoclonal antibody, 9284, resulted from from single amino acid changes either in the base of the V3 loop or in the gp120 C4 region. These amino acid changes also resulted in increased exposure of conserved epitopes overlapping the CD4 binding region. The replication-competent subset of these mutants exhibited increased sensitivity to neutralization by antibody 9284 and anti-CD4 binding site antibodies. The implied relationship of the V3 loop, which mediates post-receptor binding steps in virus entry, and components of the CD4 binding region may be important for the interaction of these functional gp120 domains and for the observed cooperativity of neutralizing antibodies directed against these regions.

Animals↗
PubMed1992

Discontinuous, conserved neutralization epitopes overlapping the CD4-binding region of human immunodeficiency virus type 1 gp120 envelope glycoprotein.

Monoclonal antibodies have been isolated from human immunodeficiency virus type 1 (HIV-1)-infected patients that recognize discontinuous epitopes on the gp120 envelope glycoprotein, that block gp120 interaction with the CD4 receptor, and that neutralize a variety of HIV-1 isolates. Using a panel of HIV-1 gp120 mutants, we identified amino acids important for precipitation of the gp120 glycoprotein by three different monoclonal antibodies with these properties. These amino acids are located within seven discontinuous, conserved regions of the gp120 glycoprotein, four of which overlap those regions previously shown to be important for CD4 recognition. The pattern of sensitivity to amino acid change in these seven regions differed for each antibody and also differed from that of the CD4 glycoprotein. These results indicate that the CD4 receptor and this group of broadly neutralizing antibodies recognize distinct but overlapping gp120 determinants.

Antibodies, Monoclonal↗
PubMed1992

Role of cAMP-dependent protein kinase in cAMP-mediated vasodilation.

In this study, the role of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) in cAMP-dependent relaxation was assessed in the isolated-perfused rat lung using a PKA inhibitor, Rp-cAMPS, 8-bromo-cAMP (8-BrcAMP), and the diterpene activator of adenylate cyclase (AC), forskolin (FSK). A role for K+ channels was also assessed with the nonselective K+ channel blocker, tetraethylammonium (TEA, 10 mM), and an ATP-sensitive K+ channel inhibitor, glibenclamide (GLI, 100 microM). Both 8-BrcAMP (0.1-1.0 mM) and RSK (0.1-10 microM) dose-dependently attenuated the peak pressor response to alveolar hypoxia (HPR). Rp-cAMPS potentiated the HPR and attenuated 8-BrcAMP-mediated vasodilation but had no effect on FSK-mediated vasodilation. FSK-mediated vasodilation was not mimicked by 1,9-dideoxy-FSK, which is biologically inactive on AC but alters K+ channels identically to FSK, nor was it attenuated by the platelet-activating factor antagonist SRI 63-441 or the cyclooxygenase inhibitor indomethacin. TEA, but not GLI, attenuated FSK-mediated vasodilation. Similarly, TEA attenuated 8-BrcAMP-mediated vasodilation. These results support roles for PKA and indirect gating of a non-ATP-sensitive K+ channel in mediating cAMP-dependent pulmonary vasodilation.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Clinical features of the idiopathic long QT syndrome.

Long QT syndrome (LQTS) is an infrequently occurring familial disorder in which affected members have electrocardiographic QT interval prolongation and a propensity to syncope and fatal ventricular arrhythmias. This review of the current literature includes discussions of inheritance, clinical presentation, diagnosis, and treatment of LQTS. At present, there are three modalities of treatment for LQTS patients: beta-blockers, pacemakers, and left cervicothoracic sympathetic ganglionectomy. Because the clinical course of LQTS is quite variable, therapy must be individualized for each patient.

Adrenergic beta-Antagonists↗
PubMed1992

Light and retinopathy of prematurity: does retinal location offer a clue?

Nursery illumination has been implicated in the pathogenesis of retinopathy of prematurity (ROP), although the results of recent studies are conflicting. The data base for this article is a prospective ROP study on 607 infants of birth weight less than or equal to 1700 g including 35 larger siblings from multiple births when 1 infant fulfilled the birth weight criteria. Retinopathy commences preferentially in the nasal retina of the most immature neonate and is less likely to develop, or its onset is delayed, in the superior and inferior regions. These findings cannot be fully accounted for by regional vascular and neuroanatomical variations. Radiometric and physiological evidence suggests that the very immature neonate, most at risk of developing severe ROP, receives the greatest retinal irradiance. Furthermore, ROP commences in the areas of the retina receiving the highest light dose, and its onset is either retarded or inhibited in the darker retinal regions. Further studies are required to determine whether early exposure to light is a factor in the development of ROP. If a causal relationship is proven, here at least is one modality that can easily and immediately be controlled.

Cohort Studies↗
PubMed1992

Cooperativity of neutralizing antibodies directed against the V3 and CD4 binding regions of the human immunodeficiency virus gp120 envelope glycoprotein.

Human immunodeficiency virus type 1 (HIV-1) infection elicits neutralizing antibodies directed against two discrete regions of the gp120 exterior envelope glycoprotein: the third variable (V3) loop and the CD4 binding region. Monoclonal antibodies directed against these two regions demonstrated additive or, in some cases, weakly synergistic neutralization of HIV-1 infection. Cooperativity in virus neutralization was also observed for some gp120 mutants that, in the absence of anti-V3 loop antibodies, were relatively resistant to neutralization by antibodies directed against the CD4 binding region. Although the binding of some anti-V3 region monoclonal antibodies increased the recognition of the multimeric envelope glycoproteins by anti-CD4 binding antibodies, this enhanced binding was not predictive of the degree of cooperativity observed in virus neutralization. These results suggest that elicitation of both types of neutralizing antibodies should increase the efficacy of vaccine preparations.

Animals↗
PubMed1992

Survival and evolution of vein grafts in otosclerosis surgery: structural and ultrastructural evidence.

The annular ligament of the stapes footplate measures 0.2 mm2 and contains elastic fibers that restrict perilymphatic movement to a molecular level. This resistance of the annular ligament prevents excessive movement of labyrinthine fluids that are potentially hazardous to the membranous and cellular structures of the inner ear. However, if the resistance of the annular ligament is overcome, then inner ear damage can occur. The vein graft, as used in our technique for otosclerosis surgery, occupies a space of 0.2 mm2 between the edge of the stapedotomy hole and the piston and has nearly the same compliance and resistance as the annular ligament of the stapes footplate. The vein graft becomes integrated with the middle-ear mucosa. It develops a rich and active blood supply and the smooth muscle cells and elastic fibers remain, although the latter show some modification of ultrastructural pattern. The graft becomes overlaid by the middle-ear epithelium. Even samples of vein graft that have been present for many years retain surviving elastic fibers, including those that have become fibrotic. In time, the number of elastic fibers increases as a result of the activity of fibroblasts, which build a poorly colored collagen.

Adult↗
PubMed1991

Probabilistic secretion of quanta in the central nervous system: granule cell synaptic control of pattern separation and activity regulation.

The implications of probabilistic secretion of quanta for the functioning of neural networks in the central nervous system have been explored. A model of stochastic secretion at synapses in simple networks, consisting of large numbers of granule cells and a relatively small number of inhibitory interneurons, has been analysed. Such networks occur in the input to the cerebellum Purkinje cells as well as to hippocampal CA3 pyramidal cells and to pyramidal cells in the visual cortex. In this model the input axons terminate on granule cells as well as on an inhibitory interneuron that projects to the granule cells. Stochastic secretion at these synapses involves both temporal variability in secretion at single synapses in the network as well as spatial variability in the secretion at different synapses. The role of this stochastic variability in controlling the size of the granule cell output to a level independent of the size of the input and in separating overlapping inputs has been determined analytically as well as by simulation. The regulation of granule-cell output activity to a reasonably constant value for different size inputs does not occur in the absence of an inhibitory interneuron when both spatial and temporal stochastic variability occurs at the remaining synapses; it is still very poor in the presence of such an interneuron but in the absence of stochastic variability. However, quite good regulation is achieved when the inhibitory interneuron is present with spatial and temporal stochastic variability of secretion at synapses in the network. Excellent regulation is achieved if, in addition, allowance is made for the nonlinear behaviour of the input-output characteristics of inhibitory interneurons. The capacity of granule-cell networks to separate overlapping patterns of activity on their inputs is adequate, with spatial variability in the secretion at synapses, but is improved if there is also temporal variability in the stochastic secretion at individual synapses, although this is at the expense of reliability in the network. Other factors which improve pattern separation are control of the output to very low activity levels, and a restriction on the cumulative size of the excitatory input terminals of each granule cell. Application of the theory to the input neural networks of the cerebellum and the hippocampus shows the role of stochastic variability in quantal transmission in determining the capacity of these networks for pattern separation and activity regulation.

Animals↗
PubMed1991

Media and methods for isolation of aeromonads from fecal specimens. A multilaboratory study.

An international multilaboratory study was conducted to establish the optimal combination of culture media, incubation time and temperature for recovery of aeromonads from stools using blood ampicillin (10 mg/l) agar (BAA), starch ampicillin (10 mg/l) agar (SAA), and cefsulodin irgasan novobiocin agar (CIN) with alkaline peptone water (APW) for enrichment. Optimal recovery of aeromonads (167/186) occurred using BAA (37 degrees C; 24 h) and CIN (25 degrees C; 48 h) with APW (25 degrees C; 24 h) subcultured to BAA (37 degrees C; 24 h) and CIN (25 degrees C; 48 h).

Aeromonas↗
PubMed1991

Protein kinase C-dependent and -independent activation of the NADPH oxidase of human neutrophils.

The protein kinase C inhibitor, staurosporine, inhibited NADPH oxidase activity of human neutrophils activated by phorbol myristate acetate. However, this inhibitor had no effect on either the initiation or the maximal rate of O2- secretion activated by the chemotactic peptide, fMet-Leu-Phe, but resulted in a more rapid termination of oxidant production. Similarly, staurosporine had no effect on the rapid (1 min) increase in luminol-dependent chemiluminescence activated by fMet-Leu-Phe, but the second (intracellular) phase of oxidant production was inhibited. The initial burst of oxidant production during phagocytosis was similarly protein kinase C-independent, but again the later phases of oxidase activity were staurosporine-sensitive. Neutrophils loaded with Quin-2 at concentrations sufficient to act as a Ca2+ buffer could not secrete O2- in response to fMet-Leu-Phe; although the initial (protein kinase C-independent) burst of luminol chemiluminescence was not observed in fMet-Leu-Phe-stimulated Ca2(+)-buffered cells, the second phase of (protein kinase C-dependent) oxidant production was largely unaffected. Hence, the initial burst of oxidant production activated by fMet-Leu-Phe, opsonized zymosan, and latex beads is independent of the activity of protein kinase C-dependent intracellular activation processes, but the activity of this kinase is required to extend or sustain the duration of oxidant production.

Alkaloids↗